This invention relates to the discovery that a group of 2-aryl-3-aroylbenzo[b]thiophenes is useful in the treatment of smoking-related bone loss.
The mechanism of bone loss is not well understood, but in practical effect, the disorder arises from an imbalance in the formation of new healthy bone and the resorption of old bone, skewed toward a net loss of bone tissue. This bone loss includes a decrease in both mineral content and protein matrix components of the bone, and leads to an increased fracture rate of, predominantly, femoral bones and bones in the forearm and vertebrae. These fractures, in turn, lead to an increase in general morbidity, a marked loss of stature and mobility, and, in many cases, an increase in mortality resulting from complications. Unchecked, bone loss can lead to osteoporosis, a major debilitating disease whose prominent feature is the loss of bone mass (decreased density and increased porosity) without a reduction in bone volume, producing porosity and fragility.
Recent studies have suggested that smoking is a risk factor for bone fractures, especially of vertebral, forearm, and hip fractures. In one study, bone density of women who smoked, or who smoked more heavily, was significantly lower than that of their twin sisters. See Hopper and Seeman, N. Engl. J. Med., 330(6), 387-392 (1994). A decrease in bone density means an increased risk of osteoporotic fractures. In a second study, bone loss was accelerated in middle-aged men who were smokers. See Slemenda et al., Ann. Intern. Med., 117, 286-291 (1992). These studies provide compelling evidence of an association between smoking and reduced bone density in both men and women.
Estrogen, either alone or combined with progestin, is currently recommended for preventing bone loss in postmenopausal women. Although estrogens have beneficial effects on bone, long-term estrogen therapy has been implicated in a variety of disorders, including an increased risk of uterine and breast cancer. Furthermore, the protective effects of estrogen therapy are eliminated for women smokers. See Kiel et al., Ann. Intern. Med., 116(9), 716-721 (1992). This lack of protection is due to smoking-related increases in the sex-hormone binding globulin and hepatic metabolism of estrogens. See Slemenda, N. Engl. J. Med., 330(6), 430-431 (1994) and Jensen et al., N. Engl. J. Med., 313(6), 973-975 (1985). Therefore, there currently exists a need for treatment of bone loss in both men and women who smoke.
The present invention provides methods for treating smoking-related bone loss, thus serving as an effective and acceptable treatment for smoking-related osteoporosis.
The 2-aryl-3-aroylbenzo[b]thiophene compounds that are used in the methods of this invention were first developed by Jones and Suarez as anti-fertility agents. See U.S. Pat. No. 4,133,814 (issued Jan. 9, 1979). These compounds are generally useful in suppressing the growth of mammary tumors.
Jones later found that a group of compounds are useful for antiestrogen and antiandrogen therapy, especially in the treatment of mammary and prostatic tumors. See U.S. Pat. No. 4,418,068 (issued Nov. 29, 1983). One of these compounds, 6-hydroxy-2-(4-hydroxyphenyl)-3-[4-(2-piperidinoethoxy)benzoyl]benzo[b]thi ophene was clinically studied for the treatment of breast cancer. This compound is called raloxifene, formerly keoxifene.